The present invention relates to a semiconductor device and a method of manufacturing the same, more specifically, a semiconductor device including a pocket region formed by tilt-angle ion implantation, and a method of manufacturing the semiconductor device.
MISFETs, to suppress the threshold voltage decrease due to the short channel effect, generally impurity doped region called a pocket or a halo (hereinafter called a pocket region) are formed by locally increasing an impurity concentration below the gate electrode.
The pocket region is formed usually by tilt-angle ion implantation in a direction tilted to the normal of a semiconductor substrate after gate electrodes have been formed on the semiconductor substrate. The pocket region is formed by the tilt-angle ion implantation.
However, as the distance between elements of different conduction types becomes smaller for higher densities of semiconductor devices, the so-called shadowing or shadow effect becomes conspicuously influential, and the ions incident on a tilted direction are shaded by a photoresist and cannot be implanted into required region.
One means of suppressing the shadowing will be thinning the photoresist film. However, the photoresist film can be thinned only in the range where the photoresist film can make the intrinsic function of masking the implantation into undesirable region. As the photoresist film is more thinned, steps below appear conspicuously as the surface steps of the photoresist film, which makes it difficult to ensure the flatness and the fine processing after the photoresist film has been applied. For these reasons, the thinning of the photoresist film is restricted.